Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/20—Pills, tablets, discs, rods
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/0087—Galenical forms not covered by A61K9/02 - A61K9/7023
  • A61K9/0095—Drinks; Beverages; Syrups; Compositions for reconstitution thereof, e.g. powders or tablets to be dispersed in a glass of water; Veterinary drenches
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
  • A61K31/495—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with two or more nitrogen atoms as the only ring heteroatoms, e.g. piperazine or tetrazines
  • A61K31/505—Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim
  • A61K31/519—Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim ortho- or peri-condensed with heterocyclic rings
  • A61K31/52—Purines, e.g. adenine
  • A61K31/522—Purines, e.g. adenine having oxo groups directly attached to the heterocyclic ring, e.g. hypoxanthine, guanine, acyclovir
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K33/00—Medicinal preparations containing inorganic active ingredients
  • A61K33/06—Aluminium, calcium or magnesium; Compounds thereof, e.g. clay
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/20—Pills, tablets, discs, rods
  • A61K9/2004—Excipients; Inactive ingredients
  • A61K9/2009—Inorganic compounds
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/20—Pills, tablets, discs, rods
  • A61K9/2004—Excipients; Inactive ingredients
  • A61K9/2022—Organic macromolecular compounds
  • A61K9/205—Polysaccharides, e.g. alginate, gums; Cyclodextrin
  • A61K9/2054—Cellulose; Cellulose derivatives, e.g. hydroxypropyl methylcellulose
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P25/00—Drugs for disorders of the nervous system
  • A61P25/04—Centrally acting analgesics, e.g. opioids
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P25/00—Drugs for disorders of the nervous system
  • A61P25/08—Antiepileptics; Anticonvulsants
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P31/00—Antiinfectives, i.e. antibiotics, antiseptics, chemotherapeutics
  • A61P31/12—Antivirals

Definitions

• the present invention relates to a water-dispersible tablet formulation containing a therapeutically active compound.
• Therapeutically active compounds or drugs are frequently administered to patients in tablet form where the drug is intended for oral administration since tablets are an especially convenient pharmaceutical form for manufacture, storage and generally usage.
• problems may arise with the administration of such tablets to patients who have difficulty in swallowing the tablets (for example, children or more seriously ill patients) especially if the tablets are large in size arising from the amount of drug required in each tablet.
• a solution to such problems is to formulate the tablets in a form whereby they can be dispersed in water to form a dispersion containing the drug which can then be drunk by the patient.
• Known water-dispersible tablets include effervescent formulations which rely on the formation of a gas to quickly break up the tablet, but these involve expensive methods of manufacture and strict regulations for such manufacture.
• Other known water-dispersible tablets use disintegrating agents such as microcrystalline cellulose used in Feldene® R dispersible tablets.
• disintegrating agents incorporated both internally and externally to the preformed granules
• sodium starch glycollate e.g. Explotab
• cross-linked povidone e.g. Kollidon CL
• a cross-linked sodium carboxymethylcellulose e.g. Ac-Di-Sol
• Swellable clays such as Veegum R and other magnesium aluminium silicates have previously been studied and proposed for use as disintegrating agents, binders and lubricants in the manufacture of tablets, but such studies and proposals were exclusively with respect to tablets intended for swallowing and not for water-dispersible tablets (Rubenstein, Pharmaceutics--The Science of Dosage Form Design (1990) for disintegrants see p 312 and 314). Moreover, there has never been any suggestion that a clay would be suitable to meet the more stringent requirements for dispersible tablets.
• Tablets for swallowing need only have a disintegration time in water of less 15 minutes and be able to form particles on disintegration in water that can pass through a 2.00 mm mesh aperture (British Pharmacopia test for swallowable tablets). Such long disintegration times and large particle sizes are entirely unsuitable for a dispersible tablet.
• a swellable clay such as Veegummust be added during granulation to meet the British Pharmacopoeia (B. P.) standard for dispersible tablets (presently set at a dispersion time of 3 minutes or less). If the swellable clay is added only after granulation the dispersion time is too high to meet the above standard.
• a water-dispersible tablet comprising a therapeutically active compound selected from the group consisting of an analgesic propionic acid derivative, a tranquillising benzodiazepine, an anti-viral nucleoside derivative (for example acyclovir), an anti-protozoal napthoquinone, allopurtnol, oxopurinol, anti-convulsant 1,2,4 triazine derivative (for example lamotrigine) and trimethoprim (optionally in combination with sulphamethoxazole), together with an effective amount of a pharmaceutically acceptable swellable clay to provide a tablet which is capable of dispersing in water within a period of 3 minutes to provide a dispersion which is capable of passing through a sieve screen with a mesh aperture of 710 ⁇ m in accordance with the test for dispersible tablets defined in the British Pharmacopoeia, 1988, Volume II, page 895.
• a therapeutically active compound selected from the group consisting of an
• the active compound employed in the tablet according to the invention is hereinafter referred to as "the active compound”.
• the present invention further provides a process for the preparation of a water-dispersible tablet comprising a therapeutically active compound selected from the group consisting of an analgesic propionic acid derivative, a tranquillising benzodiazepine, an anti-viral nucleoside derivative, an anti-protozoal napthoquinone, allopurinol, oxopurinol, anti-convulsant 1,2,4 triazine derivative and trimethoprim (optionally in combination with sulphamethoxazole), together with an effective amount of a pharmaceutically acceptable swellable clay which comprises bringing the said active compound into association with the said swellable clay to provide a water-dispersible tablet which is capable of dispersing in water within a period of 3 minutes to provide a dispersion which is capable of passing through a sieve screen with a mesh aperture of 710 ⁇ m in accordance with the test for dispersible tablets defined in the British Pharmacopoeia, 1988, Volume II, page 8
• said process comprises the steps of:
• a cylindrical disc for each tube each 20.55 to 20.85 mm in diameter and 9.35 to 9.65 mm thick, made of transparent plastic with a relative density of 1.18 to 1.20, pierced with five holes, each 2 mm in diameter, one in the centre and the other four spaces equally on a circle of radius 6 mm from the center of the disc, there being four equally spaced grooves cut in the lateral surface of the disc in such a way that at the upper surface of the disc they are 9.5 mm wide and 2.55 mm deep and at the lower surface 1.6 mm square;
• said method consisting of introducing one tablet into each of the six tubes, suspending said assembly in the beaker containing the water and operating the apparatus of a maximum period of three minutes so that all six of the tablets disperse".
• a tablet according to the invention as well as being quickly dispersible in water, has the added advantage that it meets the British Pharmacopoeia (B. P.) test for dispersible tablets in respect of dispersion times and dispersion quality (i.e. passage through a 710 ⁇ m sieve).
• B. P. British Pharmacopoeia
• the dispersion time of a tablet according to the invention is less than 2 minutes, more preferably less than 1.50 minutes and most preferably less than 1 minute.
• a further advantage of the tablets according to invention is that because a relatively fine dispersion is formed the tablet will have a lower dissolution time and thus the drug may be absorbed into the blood stream much faster. Furthermore the fast dispersion times and relatively fine dispersions obtained with tablets according to the invention are also advantageous for swallowable tablets.
• tablets according to the invention can be presented both for dispersion in water and also for directly swallowing.
• Those tablets according to the invention that are intended for swallowing are preferably film-coated to aid swallowing. Such film-coating however increases the dispersion time up to 5 minutes determined in accordance with the above-mentioned B. P. test.
• a water-dispersible film-coated tablet comprising a therapeutically active compound selected from the group consisting of an analgesic propionic acid derivative, a tranquillising benzodiazepine, an antiviral nucleoside derivative, an anti-protozoal napthoquinone, allopurinol, oxopurinol, an anti-convulsant 1,2,4-triazine derivative and trimethoprim (optionally in combination with sulphamethoxazole), together with an effective amount of a pharmaceutically acceptable swellable clay to provide a film-coated tablet which is capable of dispersing in water within a period of 5 minutes to provide a dispersion which is capable of passing through a sieve screen with a mesh aperture of 710 ⁇ m in accordance with the above-defined British Pharmacopoeia test for dispersible tablets subject to the variation of the said period specified in the test from 3 minutes to 5 minutes.
• a therapeutically active compound selected from the group consisting of
• the particle size distribution of the dispersion particularly when the active compound is acyclovir are set out in the following table with the increasingly preferred values being quoted from left to right.
• active compounds which have been employed in the tablets according to the invention are listed below together with respective patent publications, (in appropriate instances) which teach how to make them and infections or medical conditions which can be treated by them (incorporated by reference): acyclovir (UK No.1523865), lamotrigine (EP Nos. 021 121 and 247 829), diazepam, paracetamol, (both commercially available), 1-( ⁇ -D-arabinofuranosyl)-5-propy-1-ynyl-uracil (EP No. 0272 065), 2-[4-(4-chlorophenyl)cyclohexyl]-3-hydroxy-1,4-naphthoquinone (EP No. 0123 238), allopurinol (G. B. No. 1445 983).
• acyclovir UK No.1523865
• lamotrigine EP Nos. 021 121 and 247 829
• diazepam paracetamol
• paracetamol both commercially available
• Examples of other active compounds include: 3'-azido-3'-deoxythymidine (EP No. 0196 185), 5-prop-1-ynyl-1-(5-trimethylacetyl- ⁇ -D-arabinofuranosyl)uracil (EP No. 0375 164), 2-(2-amino-1,6-dihydro-6-oxo-9H(purin-9-yl)methoxy)ethyl-valinate (EP No. 0308 065), 2',3'-dideoxy-5-ethynyl-3'-fluorouridine (EP No.
• the active compound is lamotrigine, i.e. (3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine, more preferably acyclovir or pharmaceutically acceptable salts of these compounds which have acceptable dispersibility in water.
• lamotrigine i.e. (3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine
• a suitable salt of lamotrigine is the isethionate salt (i.e. 2-hydroxymethanesulphonate).
• swellable clay as used herein includes layered clays (such as smectites), porous fibrous clay minerals, and synthetic clay materials related in structure to layered clays and porous fibrous clays.
• layered clays as used herein includes substantially homogeneous layered clays and mixtures thereof, and interstratified or mixed layered clays.
• Substantially homogeneous layered clays includes the smectite group for example dioctahedral and trioctahedral types.
• dioctahedral smectites are the montmorillonite group (montmorillonoids); magnesium and other (e.g. calcium) aluminium silicates such as Veegum in its various grades e.g. Veegum, Veegum HV, Veegum F, and Veegum WG); almasilate; fullers earth (e.g.
• triocatahedral smectites also known as saponites
• Swinefordite hectorire
• stevensite examples of smectites containing more unusual elements are Volkhonsite, Medmontite, Sauconite, nickel smectites and vanadium smectites.
• smectites containing more unusual elements are Volkhonsite, Medmontite, Sauconite, nickel smectites and vanadium smectites.
• related smectites such as vermiculites may also have application.
• interstratified or mixed layer clays includes clays involving different layers arranged in a regular or irregular structure.
• the most common examples of such clays have generally two components in substantially equal proportions and have been given mineral names such as rectorite (mica-smectite), hydrobiotite (biotite-vermiculite), corrensiten (chlorite-smectite) allettite (talc-saponite). More irregular arrangements include illite-smectite, chlorite-smectite, and kaolinite-smectite.
• interstratified clays are tosudite, tarasovite, allevardite, Japanese bentonite ("acid clays"), AWAZU acid clay, and kaolinite-smectite.
• Other mixed layer clays may include one or more of the following minerals: clinchlore, chamosite, nimite, thuringite, sudoite, and cookeite.
• Mixed layer smectities are also known e.g. interdispersed montmorillonite and beidellite layers.
• the layers of mixed layer clays may be homogeneous or non-homogeneous.
• porous fibrous clays includes palygorskite and sepiolite such as, for example attapulgite and American fuller's earth.
• synthetic clay materials includes materials related in structure to layered clays and porous fibrous clays such as synthetic hectorire (lithium magnesium sodium silicate) for example laponite R .
• clays have application alone or in combination and in mixed layer clays: kaolinires, serpentines, pyrophyllites, talc, micas and brittle micas, chlorites, smectites and vermiculites, palygorskites and sepiolites.
• phyllosilicates clay minerals which may be employed in the tablets according to the invention are allophane and imogolite.
• the swellable clay is a pharmaceutically acceptable crystalline mineral clay having a lattice structure which expands upon hydration, preferably a pharmaceutically acceptable smectite or attapulgite clay, especially a montmorillonoid, more preferably yet a montmorillonoid chosen from the group consisting of montmorillonite, sauconite, vermiculite, bentonire and hectorire, still more preferably an aluminium magnesium silicate and most preferably Veegum R .
• a pharmaceutically acceptable crystalline mineral clay having a lattice structure which expands upon hydration preferably a pharmaceutically acceptable smectite or attapulgite clay, especially a montmorillonoid, more preferably yet a montmorillonoid chosen from the group consisting of montmorillonite, sauconite, vermiculite, bentonire and hectorire, still more preferably an aluminium magnesium silicate and most preferably Veegum R .
• smectine as used herein in relation to tablets of the present invention includes the smectites as exemplified herein and with reference to O'Brian P. and Williamson C. J., in "Clays and Clay Minerals vol. 38 No. 3 pp322-326, 1990" and the other clay nomenclature references set out hereinbefore.
• magnesium aluminium silicate as used herein in relation to tablets of the present invention should be understood to include the Aluminium Magnesium Silicate defined in the British Pharmacopoeia, volume 1, pages 27-28, 1988 and the Magnesium Aluminium Silicate defined in the United States Pharmacopoeia, National Formulary XVI, pages 1943-1944, 1990.
• said silicate is in the form of a microfine powder having a No. 325 US Standard mesh particle size, a viscosity of 250 cps ( ⁇ 25%) for a 5.5% (w/v) aqueous dispersion and an acid demand (the volume in ml.
• VEEGUM F R. T. Vanderbilt Co., New York, N.Y., U.S.A.; K & K-Greeff Chemicals Ltd., Croydon, Surrey CR9 3QL, England.
• the amount of swellable clay employed in the tablet according to the invention generally depends on the weight of the tablet. Experiments with acyclovir indicate for a 100 mg tablet, amounts as low as 0.25% w/w of tablet can be used whereas for tablets of about 1000 mg to 1200 mg up to 60% w/w, advantageously up to 50% w/w preferably up to 40% w/w could be used to give a satisfactory dispersible tablet in accordance with the invention. Other practical considerations such as poor flow and compression properties may, however, limit the maximum percentage weight of clay which can be incorporated within any given weight of tablet. In our experiments up to 40% w/w of swellable clay was used for a tablet having a total weight of 1100 mg and gave fine dispersions and fast dispersion times.
• the intra-granular amount of swellable clay such as a crystalline mineral clay for example, magnesium aluminium silicate is suitably present in the following general ranges 0.25 to 60% w/w, preferably 0.25 to 50% w/w, more preferably 0.5 to 50% w/w, more preferably still 1 to 50% w/w, more preferably still 1 to 40% w/w, more preferably still 2 to 20% w/w, more preferably still 2.5 to 20% w/w, still more preferably 3 to 10% w/w, and most preferably 5 to 10%, most desirably about 5% w/w.
• the tablets according to the invention will generally contain a pre-determined amount of the active compound, depending on the identity of the compound, the desired dosage and the total weight of the tablet.
• the tablets When the active compound is acyclovir, the tablets generally contain 100 to 1000 mg, preferably 200 to 800 mg, such as 400 to 800 mg of the compound. Such dosage units may be administered one or more times, for example up to five times, per day, at the discretion of the physician, according to the age and condition of the patient and the particular condition being treated.
• the swellable clay e.g. Veegum F, is preferably present in an amount of 40 to 120 mg intragranularly.
• the tablets according to the invention conveniently contain 2.5 to 500 mg. desirably 5 to 250 mg. of lamotrigine calculated as lamotrigine base.
• Preferred said unit doses include 5 mg., 12.5 mg., 25 mg., 50 mg., 100 mg., 150 mg., 200 mg. and 250 mg., calculated as the base.
• the swellable clay e.g. Veegum F
• the swellable clay is preferably present in an amount of 2 to 4 mg, especially about 3 mg.
• the swellable clay e.g. Veegum F
• the swellable clay is preferably present in amount of 5 to 20 mg, especially about 12 mg.
• the tablets according to the invention contain the active compound in the following percentage proportions:
• Paracetamol--50 to 904 w/w preferably 60 to 754 w/w
• Pseudoephedrine--5 to 50% w/w, preferably 15 to 30% w/w
• Dextromethorphan--2 to 20% w/w, preferably 5 to 15% w/w
• Acrivastine--1 to 10% w/w, preferably 2 to 5% w/w
• Guaiphenesine--10 to 40% w/w, preferably 15 to 30% w/w
• the active compound such as acyclovir
• the dispersion time remains substantially constant over a range of tablet hardnesses. This is a considerable quality control advantage since in industrial manufacture it is essential to maintain a constant tablet hardness. Tablets according to the invention can thus be produced with sufficient hardness and friability so that they can easily be film-coated.
• a tablet according to the invention should desirably have a friability of about 2% or less, preferably 0.5% or less.
• excipients suitable for inclusion in the tablets according to the invention include the following:
• Binders and Adhesives we have found e.g. with acyclovir tablet formulations that if there is sufficient amount of swellable clay such as Veegum F present within the granules, then a separate binder is not required (i.e. the clay also acts as a binder). Preferably however a separate binder is present in a sufficient amount to provide a tablet having a satisfactory tablet hardness and satisfactory dispersion characterstics.
• the amount of binder will vary depending on the overall tablet formulation and type of binder used but general functional limits for most tablets of the invention are 0 to 25% w/w.
• the following binders and amounts are suitable for inclusion in a tablet according to the invention.
• binders are: acacia mucilage 0 to 25% w/v, preferably 1 to 5% w/v, alginic acid 0 to 20.0% w/v, preferably 1 to 5% w/v, polyvinylpyrrolidone (povidone) 0 to 15.0% w/v, preferably 0.5 to 5% w/v, gelatin 0 to 20.0% w/v, preferably 1 to 5.0% w/v, sucrose 0 to 70.0% w/v, preferably 2.0 to 20.0% w/v, starch mucilage 0 to 10.0% w/v, preferably 0.5 to 5.0% w/v, pregelatinised starch 0 to 10.0% w/v, preferably 0.5 to 5.0% w/v, star
• zein 0 to 30% w/v preferably 1 to 10% w/v, hydroxyethyl cellulose 0 to 5% w/v, preferably 2 to 4% w/v, hydroxypropyl cellulose up to 5% w/v, preferably 2 to 4% w/v, methyl cellulose up to 20% w/v, preferably 1 to 10% w/v, polymethacrylates up to 25% w/v, preferably 5 to 10% w/v, carboxymethylcellulose calcium 0 to 20% w/v, preferably 5 to 10% w/v.
• Disintegrating agents Tablets according to the invention can be formulated in the absence of separate disintegrating agents although their inclusion may be advantageous for their disintegration in water as an adjunct to the dispersion afforded by the clay above.
• suitable disintegrating agents which can optionally be incorporated into a tablet according to the invention are: microcrystalline cellulose (e.g. Avicel R) 0 to 30% w/w, preferably 5 to 10% w/w, Sodium carboxymethyl cellulose (e.g. Nymcel R) 0 to 5% w/w, preferably 1 to 2% w/w, calcium carboxymethyl cellulose 0 to 20% w/w, preferably 1 to 5% w/w, modified cellulose gum (e.g.
• Ac-Di-Sol R 0 to 10% w/w, preferably 1 to 5% w/w, cross-linked povidone 0 to 10% w/w, preferably 2 to 6% w/w, alginic acid and alginates 0 to 10% w/w, 2 to 5% w/w, pregelatinised starch 0 to 10% w/w, preferably 0.5 to 5% w/w, sodium starch glycollate (e.g. Explotab R, Primojel R) 0 to 10% w/w, preferably 0.5 to 5% w/w, modified corn starch (e.g. starch 1500 R) 0 to 20% w/w, preferably 1 to 10% w/w, starch (e.g.
• potato/maize starch 0 to 15% w/w, preferably 0.2 to 10% w/w, ion exchange resin such as polacrin potassium (e.g. Amberlite IRP-88) up to 5% w/w, preferably 0.5 to 2.0% w/w.
• ion exchange resin such as polacrin potassium (e.g. Amberlite IRP-88) up to 5% w/w, preferably 0.5 to 2.0% w/w.
• Fillers serve the purpose of bulking up the tablet to a suitable size and aiding compressibility especially in lower dosage tablets.
• the amount of filler depends on its type, size of tablet and amount of active compound. When the concentration of active compound is below 60% w/w, more preferably 45% w/w and most preferably below 30% w/w, an inorganic water-insoluble filler is advantageously used.
• water-soluble fillers (which can be used in general quantities of 0 to 95% w/w) are: soluble lactose, compressible sugar, confectioners sugar, dextrose, mannitol, sodium chloride, sorbitol, xylitol, sodium chloride F.
• water-insoluble fillers which can be used in general quantities of 0 to 93% w/w
• examples of water-insoluble fillers are: calcium carbonate, magnesium carbonate, calcium phosphate (e.g. di and tri basic calcium phosphate), calcium sulphate, kaolin, microcrystalline cellulose, powdered cellulose, pregelatinized starch 5 to 75%, starch, barium sulphate, magnesium trisilicate, aluminium hydroxide.
• a filler having a negative heat of solution in water for example mannitol, sorbitol and xylitol
• mannitol, sorbitol and xylitol provide tablets which, in addition to being water-dispersible, are especially suitable for chewing in the mouth, the dissolving of such an excipient in the saliva producing a cool, pleasant sensation.
• Lubricants Generally lubricants are used in as low an amount as possible. Examples of lubricants with percentage weights which are suitable for a tablet are: stearates (e.g. magnesium or calcium stearate) 0.2 to 5% w/w, preferably 0.25 to 1% w/w, talc 0.19 to 5% w/w, preferably 1 to 2% w/w, polyethylene glycol 0.19 to 5% w/w, preferably 2 to 5% w/w, liquid paraffin 0.18 to 5% w/w, preferably 2 to 5% w/w, sodium lauryl sulphate 0.19 to 5% w/w, preferably 0.5 to 2% w/w, magnesium lauryl sulphate 0.12 to 5% w/w, preferably 1 to 2% w/w, colloidal silicon dioxide 0.1 to 5% w/w, preferably 0.1 to 1.0% w/w, palmitostearate 0.01 to 5% w/w,
• wetting agents/surfactants examples with suitable amounts are: sodium dodecyl sulphate 0 to 10% w/w, preferably 0.5 to 2% w/w, sodium lauryl sulphate 0 to 10% w/w, preferably 0.1 to 3.0% w/w, polyoxyethylene sorbitan fatty acid esters (Tweens) 0 to 3% w/w, preferably 0.05 to 1.0% w/w, polyoxyethylene stearates 0 to 2% w/w, preferably 0.05 to 1.0% w/w, sorbitan fatty acid esters (Spans) 0 to 3% w/w, preferably 0.05 to 1.0% w/w.
• Glidants for example, talc 0 to 5% w/w, preferably 1 to 2% w/w, starch 0 to 15% w/w, preferably 2 to 10% w/w, magnesium stearate up to 5%, preferably 0-2.0% w/w, silica derivatives generally 0 to 1% w/w, preferably 0.2 to 0.5% w/w, such as colloidal silica (e.g.
• Aerosil 0 to 0-5% w/w, preferably 0.25 to 3% w/w, pyrogenic silica 0 to 2% w/w, preferably 0.25 to 1% w/w, hydrated sodium silicoaluminate 0 to 2% w/w, preferably 0.5 to 1% w/w, colloidal silicon dioxide 0 to 0.5% w/w.
• Flavouring agents are used in for example approximate quantities of 0 to 5% w/w, preferably 0.25 to 2% w/w, orange, cherry and strawberry, raspberry, grape and passion fruit.
• Sweetening agents for example sodium saccharin 0 to 10% w/w, preferably, 0.5 to 5.0% w/w, aspartame 0 to 10% w/w, preferably 0.25 to 5.0% w/w, confectioners sugar 0 to 30% w/w, preferably 5 to 20% w/w, sorbitol 25 to 90% w/w, preferably 0.5 to 10% w/w, sucrose 0 to 85% w/w, preferably 0.5 to 20% w/w, xylitol 0-20% w/w, preferably 0.5 to 10% w/w.
• sodium saccharin 0 to 10% w/w, preferably, 0.5 to 5.0% w/w, aspartame 0 to 10% w/w, preferably 0.25 to 5.0% w/w, confectioners sugar 0 to 30% w/w, preferably 5 to 20% w/w, sorbitol 25 to 90% w/w, preferably 0.5 to 10% w/w, sucrose
• Such materials may be incorporated at the appropriate stage(s) of the manufacturing process together with any other agents (e.g. colourants).
• the dry mixing is effected with a mixing time of 5 minutes to 25 minutes preferably about 10 minutes.
• the swellable clay can be dry mixed with the active compound and other excipients and then granulating solution added, or the clay and other excipients can be dispersed firstly in the granulating solution and then added to the active compound and any other excipients prior to granulation.
• the liquid employed to moisten the dry mixture, prior to the granulation step is preferably aqueous, for example water or a mixture of water and a suitable alcohol such as ethanol or isopropanol.
• Suitable granule drying times and conditions are about 50° to 80° C., (using a dryer such as with a tray or fluid bed dryer) to obtain a moisture content generally below about 4%.
• compression weights and final table hardness will vary according to the size of tablet, but generally suitable values are as follows;
• the tablets may optionally be film-coated, for example with hydroxypropylmethyl cellulose, polyethylene glycol or titanium dioxide, and/or may be scored and/or may be polished, for example with polyethylene glycol 8000. If the tablets are film-coated, this makes them easier to swallow or chew (i.e. the tablets are suitable for either dispersion in water or for direct swallowing or chewing), but the dispersion time is increased.
• the present invention also provides:
• the swellable clay of the invention is a pharmaceutically acceptable crystalline mineral compound, such as aluminium magnesium silicate (e.g. Veegum).
• aluminium magnesium silicate e.g. Veegum
• the therapeutic use of a tablet of the invention includes both treatment and prophylaxis.
• the invention has been found to have particular application with lamotrigine because of the long term instability of lamotrigine in aqueous media. Furthermore dispersible tablets containing lamotrigine have been found to give a finer dispersion than tablets using more common disintegrating agents such as Explotab.
• Granules suitable for use in the preparation of a water-dispersible compressed tablet, comprising lamotrigine or a pharmaceutically acceptable salt thereof together with a pharmaceutically acceptable crystalline mineral clay as dispersing agent;
• a water-dispersible tablet comprising lamotrigine or a pharmaceutically acceptable salt thereof together with a pharmaceutically acceptable crystalline mineral clay having a lattice structure which expands upon hydration as dispersing agent.
• the lamotrigine or a pharmaceutically acceptable salt thereof together with the mineral clay are comprised within the tablet in granulated form.
• lamotrigine or a pharmaceutically acceptable salt thereof and the pharmaceutically acceptable crystalline mineral clay which may be chosen from the group consisting of attapulgite, smectite and montmorillonoid clays or magnesium aluminium silicate,
• fillers eg lactose, avicel or mannitol
• disintegrants e.g., binders, etc.
• a method for the treatment in a human being of a disorder of the central nervous system which comprises administration of a water-dispersible compressed tablet comprising lamotrigine or a pharmaceutically acceptable salt thereof together with a pharmaceutically acceptable crystalline mineral clay as dispersing agent.
• Especially preferred tablets are those wherein the lamotrigine is present as the base.
• the said tablets may be employed in human medicine in the treatment of disorders of the central nervous system and in particular in the treatment of epileptic seizures. They may be administered one or more times per day, for example up to five times per day, at the discretion of the attendant physician and dependent upon the age and condition of the patient, the particular disorder being treated, the unit dose adopted and the total dose required.
• a suitable daily dose for the treatment of epileptic seizures will generally lie in the range of 5 to 500 mg., more often in the range of 25 to 400 mg., calculated as the base.
• the physical size of the said tablets is desirably such as to permit their dispersion, prior to oral ingestion, in an acceptably small volume of water.
• a tablet containing 5 mg. (calculated as the base) of lamotrigine or a salt thereof, a dose especially suitable for paediatric use, is advantageously small enough to disperse in the volume of water held in a standard 5 ml. medicine spoon.
• Tablets of the invention containing lamotrigine (or a salt thereof) advantageously include a magnesium aluminium silicate such as Veegum F as the swellable clay together with further optional pharmaceutical carriers or excipients referred to above such as binders, lubricants, fillers, disintegrating agents etc.
• a magnesium aluminium silicate such as Veegum F as the swellable clay
• further optional pharmaceutical carriers or excipients referred to above such as binders, lubricants, fillers, disintegrating agents etc.
• ingredients are advantagously present in the following proportions: lamotrigine: 2% w/w to 90% w/w preferably 5% w/w to 40% w/w; swellable clay: 0.25% w/w to 40% w/w preferably 0.25% w/w to 10% w/w.
• a suitable formulation of a dispersible tablet containing 25 to 200 mg lamotrigine would be:
• a suitable formulation of a dispersible tablet containing 5 mg to 50 mg of lamotrigine would be as follows, (values being in % w/w).
• the present invention is particularly applicable to the formulation of water-dispersible tablets containing acyclovir as the active compound.
• Acyclovir is a compound which has been found to have potent activity against viruses of the herpes family, particularly herpes simplex and herpes varicella zoster. Such activity has been demonstrated by the outstanding success of acyclovir in the therapeutic treatment of clinical conditions such as genital herpes caused by the herpes varicella zoster virus.
• acyclovir In the treatment of certain conditions, it may be necessary to administer acyclovir to the patient in relatively large dosages to achieve the effective therapeutic levels of drug in the plasma, particularly when oral administration is desired.
• acyclovir In the treatment of shingles, it is recommended to administer acyclovir at a dosage regime of 800 mg five times per day.
• a tablet formulation containing 800 mg of acyclovir is currently available but its relatively large size sometimes renders it difficult to swallow by elderly patients, such patients being particularly susceptible to shingles. This problem is obviated by the water-dispersible tablets according to the invention which enable relatively high doses of acyclovir to be administered in a drinkable dispersion by the oral route.
• the advantageous water-dispersibility of tablets according to the invention containing acyclovir as the active compound is especially surprising in view of the poor water-dispersibility demonstrated by tablets containing conventional disintegrating agents such as sodium starch glycollate, cross-linked povidone and cross-linked sodium carboxymethylcellulose.
• a granulate comprising acyclovir together with a pharmaceutically acceptable magnesium aluminium silicate compound
• a water-dispersible pharmaceutical tablet formulation comprising acyclovir together with a pharmaceutically acceptable magnesium aluminium silicate compound.
• a process for the preparation of a pharmaceutical tablet formulation which comprises admixing acyclovir with a magnesium aluminium silicate compound and optionally one or more further pharmaceutical carriers or excipients, granulating the resulting mixture with a pharmaceutically acceptable liquid, drying the resulting granulate, optionally mixing the dried granulate with one or more further pharmaceutical carriers or excipients, and subsequently compressing the dried granulate to form tablets.
• the liquid employed in the above granulation step is advantageously aqueous, for example, an aqueous ethanol mixture.
• the resulting tablets may be subsequently film coated for example with hydroxypropylmethyl cellulose, titanium dioxide or polyethylene glycol and, if desired, polished for example with polyethylene glycol 8000.
• Tablets according to the invention containing acyclovir advantageously include a magnesium aluminium silicate such as Veegum F as the swellable clay optionally together with further pharmaceutical carriers or excipients referred to above such as disintegrating agents, binders, fillers, lubricants etc.
• a magnesium aluminium silicate such as Veegum F as the swellable clay
• further pharmaceutical carriers or excipients referred to above such as disintegrating agents, binders, fillers, lubricants etc.
• ingredients are advantageously present in the following proportions: acyclovir 40 to 98% w/w, preferably 75 to 85% w/w, swellable clay 0.5 to 40% w/w, preferably 0.5 to 10% w/w.
• a suitable formulation of an acyclovir dispersible tablet containing from 200 mg-800 mg acyclovir would be:
• Examples 1 to 6 and 29 are comparative examples while examples 7-28, 30 and 31 describe the preparation of tablets according to the invention in which the active compound is acyclovir.
• Example 7 In accordance with the invention, to illustrate that the disintegration time remains substantially constant at different tablet hardnesses, the formulation of Example 7 was compressed at approximately 8 kp (7a), 12 kp (7b) and 18 kp (7c) and the results noted hereafter.
• Examples 32-40 describe the preparation of tablets according to the invention in which the active compound is lamotrigine.
• This granule can be used to make other strengths of acyclovir dispersible tablets, e.g. 200 mg and 400 mg, compressing the dried granules to a weight of respectively 263 mg and 526 mg, using round punches with diameters of respectively 8.6 mm and 11.0 mm.
• Steps (a) to (f) described in Example 8 were repeated to form an uncoated tablet which was then film-coated by the following procedure.
• the film-coating apparatus used was a Manesty Accellacota 10.
• the coating suspension was sprayed onto the tablet cores to a target weight increase of between 0.5-1.0% using suitable parameters of:
• a polish coat of PEG8000 was then applied to the film-coated tablets, to a further weight gain of 0.1-0.2%.
• Example 13 Acyclovir, Avicel PH101, Sodium starch glycollate and Veegum F are dry mixed in a mixer. The mixture is then granulated after adding a sufficient volume of 50% aqueous alcohol (IMS). The resulting granules are dried, blended with the magnesium stearate and then compressed to form tablets.
• IMS aqueous alcohol
• Example 13 The procedure described in Example 13 for the preparation of the granules and formation of the tablets is employed except that granulation of the dry mixture is effected with the Povidone in a 50% aqueous alcohol solution.
• Film coating of the resulting tablets can be optionally effected by treating the tablets with a dispersion of Opadry white dispersion in purified water and drying the coated tablets which are subsequently polished with a solution of polyethylene glycol 8000, USNF in 50% aqueous alcohol (IMS).
• IMS 50% aqueous alcohol
• Example 15 the procedure described in Example 13 for the preparation of the granules and formation of the tablets is employed except that granulation of the dry mixture was effected with the Povidone in a 50% aqueous alcohol solution.
• Flavouring agents may be added at blending step (g) above.
• the lamotrigine tablets could be optionally film coated using the same procedure as described for Example 9.
• the residual moisture content of the granule (LOD) was determined on a 3-4g sample using a Computrac moisture analyser set to 90° C. operated in accordance with the manufacturer's procedure.
• a 10 g sample of granule was sifted for 2 minutes at suitable pulse and sift amplitudes in an Allen Bradley sonic sifter in accordance with manufacturer's instructions. Sieves of 710 ⁇ m, 500 ⁇ m, 355 ⁇ m, 250 ⁇ m, 150 ⁇ m, 106 ⁇ m and 53 ⁇ m were used. The WMD was calculated from the cumulative percentage undersize size distribution using a computer programme.
• a particle size analysis was carried out on the dispersion of a tablet of Example 9 in accordance with the following method.
• the particle size distribution was determined using a Malvern 2600 particle analyser as follows. The instrument was set to analyse particles in liquid with magnetic stirrer fitted. A 300 mm focal length lens was used.
• the particle size distribution was as follows:

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